Construction Of Crystal Morphology And Study On Precipitation Process Of Thiamine Nitrate

Thiamine nitrate is of special value for food enrichment and multi-vitamin preparations. Up to now, homemade thiamine nitrate products are not as good as thoseoverseas products in terms of its purity, size, etc. Because of poor quality, domestic products are incapable of competing with overseas products for thiamine nitrate market,and national factories are forced to take measures to improve qualities of their products.For synthesize of thiamine nitrate, crystallization unit is one of main processes that decide the quality, processes and uses of products. Therefore, to improve the quality of thiamine nitrate, it is significant to investigate the crystallization process of thiamine nitrate. In this paper, a systematic research work about crystallization process of thiamine nitrate has been completed.Firstly, a perfect morphology of thiamine nitrate crystal was constructed by means of experiment. The influences of all kinds of factors on the crystalline morphology of product were studied deeply. The crystal structure of thiamine nitrate was measured by the X-ray diffraction. Based on the XRD data, its morphology was well studied by BFDH model and AE model. The result of BFDH model was in agreement with the actual morphology. Secondly, the systematic thermodynamics characteristics including solubility, metastable zone and induction period of thiamine nitrate were measured during the thermodynamics study. The nucleation and crystal growth behavior was particularly observed during crystallization kinetics study, and the mathematics models that described nucleation rate and growth rate of thiamine nitrate crystal were established. Primary nucleation was the main nucleation mode in the precipitation process. However, secondary nucleation cannot be ignored when the slurry density is high, and the supersaturation is low. It was concluded that the crystal growth was size-dependent and controlled by diffusion and surface reaction. In addition, the activated energy of nucleation, the activated energy of crystal growth and some other dynamic parameters were regressed based on the experimental data.Finally, a population balance model that can describe the population density of precipitation process of thiamine nitrate was established on the basis of population balance equation and kinetics equation. On the foundations of modeling and experimental study, the crystallization process of thiamine nitrate in laboratory-scale was optimized. According to the optimum operation schedule, crystal products are up to the pharmaceutical standard of USP and BP, and reached the international level. The purity of our products(99.5%) exceeded that of domestic products by 0.3%, the yield exceeded by 1.5%, and the medium size was fourfold as that of domestic products. The crystal of perfect morphology exceeds the same products overseas in crystal habit , C.V. of CSD and purity.